The present invention relates to new heterocyclic compounds, production and use thereof. The compounds are especially useful as therapeutics of brain dysfunction.
2. Description of the Prior Art
A profile of diseases is changing greatly due to a rapid increasing population of an old-age people. A senile dementia among various gerontodiseases is one of the most important study subjects from both of the social and medical viewpoints One of the medical measures for this senile dementia is to develop therapeutic drugs. Cerebral vasodilators and metabolism enhancers or agents for improving the function of cerebral neuronal transmitters have been used as therapeutic agents for senile dementia.
However, therapeutic agents for senile dementia which have been used so far could not give a satisfactory clinical efficacy. One of the biggest reasons for it was that these therapeutic agents either have an insufficient effect or have no efficacy at all against memory disorder which is the main symptom of a senile dementia. It makes it more difficult to create truly effective agents in this field that the cause of senile dementia (particularly Alzheimer's type of dementia) and the critical mechanism for memory disorder have not yet been sufficiently clarified.
However, the physiological study of brain made it clear that there is a close relation between functional disorder of cerebral cholinergic neuron and memory disorder, and a possibility was suggested that an activator for cerebral cholinergic function may become the therapeutic agent for dementia but nobody has succeeded so far in developing the drugs while the clinical trials are ongoing.
Other physiological findings to overcome the aforesaid subject is that an intracerebral amino acid, particularly glutamate, has a very important role to form a memory. Intracerebral receptors of glutamate are mainly classified into three sub-types and those are NMDA (N-methyl-D-aspartate)-type, quisqualate-type and kainate-type. It is presumed that the action of glutamate on the NMDA-type receptor among these receptors is important to form a memory. This presumption is based upon the very important new medical finding that the stimulation by glutamate of the NMDA-type receptor participates in the mechanism to form a physiological phenomenon of long term potentiation at the hippocampus in the brain [Teyler, T. J. and Discenna, P., Ann. Rev. Neurosci., 10:131-161, 1987; Cotman, C. W. and Monagham, D. T. Ann Rev. Neurosci., 11:61-80, 1988]. However, it is considered that a participation of the other sub- type receptors can not be denied completely.